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Eddy Flux Measurements, Ridge Station, Imnavait Creek, Alaska - 2014

Abstract:

In contribution to the Arctic Observing Network (AON), the researchers have established two observatories of landscape-level carbon, water and energy balances at Imnavait Creek, Alaska and at Pleistocene Park near Cherskii, Russia. These will form part of a network of observatories with Abisko (Sweden), Zackenburg (Greenland) and a location in the Canadian High Arctic which will provide further data points as part of the International Polar Year. This particular part of the project focuses on simultaneous measurements of carbon, water and energy fluxes of the terrestrial landscape at hourly, daily, seasonal and multi-year time scales. These are the major regulatory drivers of the Arctic climate system and form key linkages and feedbacks between the land surface, the atmosphere and the oceans. We will provide a comprehensive description of the state of the regional Arctic system with respect to these variables, its overall regulation and controlling features and its interaction with the global system.In support of these objectives, a 3m eddy covariance station was established on a low ridge adjacent to Imnavait Creek, Alaska. This station has been continuously monitoring carbon dioxide, water vapor, energy fluxes and various micrometeorological variables.

Keywords:

Arctic LTER keywords:

Date Range:

Wednesday, January 1, 2014 to Thursday, December 31, 2015

Publication Date:

Friday, December 12, 2014

Methods:

There are two types of data that are collected from each flux station involved in the AON project: high frequency eddy covariance (EC) data and low frequency means of meteorological and subsurface data. On a daily basis, approximately 75Mb of high frequency binary data and 16Kb of low frequency ASCII data is collected.

This station uses a CR3000 data logger and a laptop to collect and store data. The CR3000 is used to measure the open-path EC equipment which is sampled at 10Hz. Micrometeorological data is scanned at 0.33Hz and all data points are averaged every half hour. The CRBASIC program that controls the data logger has been written in such a way that only the most basic corrections and filtering are applied to the raw data. These would include shifting the CSAT3 and LI7500 data arrays by 2 and 3 scans respectively to account for the inherent processing delays of these sensors.

The high frequency data is processed to yield mass and energy fluxes using a Reynold's decomposition after which the following corrections are applied: the WPL correction, a coordinate rotation, a spectral correction and the 'Burba' correction. Further quality controls flags are generated such as a stationarity test and a foot print analysis.

The high frequency processed tables are then combined with the low frequency micrometeorological data after which the data is both filtered and gap-filled. The following procedures are used to filter the data:

1) Parameters that are based on the engineering specifications of each instrument. This normally involves filtering data based on the operating temperature range.2) Parameters that are based on the Automatic Gain Control of the LI7500 (AGC - lens transmissivity flag). If this value exceeds a given threshold, the lens of the LI7500 is assumed to be obstructed by ice or snow. All measurements from this sensor and all radiation sensors are then assumed to be similarly obstructed and this data is filtered.3) Any sources of air flow distortion are identified at each site and all EC measurements from those azimuth directions are filtered. Thus, if any wind that originates between these wind rejection angles, then this EC data is filtered out.4) Parameters for impossible measurements (i.e. negative values from a precipitation gauge or pyranometer.)5) Parameters for previously flagged data including '-9999'. Data loggers or other processed datasets for which raw data isn't available will sometimes have various flag strings in use. This will standardize everything to 'NaN'.6) A three-standard deviation filter to get rid of extreme outliers.7) A similarity/cluster filter - With certain instruments, the appearance of a string of identical values in a time series usually indicates measurement errors. Any time series with clusters of 5 identical values are filtered.

The following procedures are used to gap-till the data:1) A Pth order autoregressive model. Two values for each missing element in a time series are predicted with a forward-looking model and a back-looking model. This function is currently looking 168 elements in both directions in a time series and both predictions are averaged to produce a final estimate. This model is still capable of producing impossible values (i.e. negative measurements from a pyranometer) which are filtered out - thus, there may still be gaps in the time series, but they will be minimized.2) Filtered values from the beginning and end ranges of a time series are predicted using a variant of the MDV method wherein values are estimated using binned half-hourly averages from the following or the previous seven days.

See the file 2014_IC_1991_metadata_20141231.csv for data collection statistics.

Definition: FC_cwu_f with Burba correction only if Tair below -1C and NEE negative

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

FC_cwbNEGu_gf

Label: FC_cwbNEGu_gf

Definition: FC_cwbNEGu_f gap-filled

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_FC_cwbNEGu_gf

Label: qc_FC_cwbNEGu_gf

Definition: qc value of FC_cwbNEGu_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

LE_cw_f

Label: LE_cw_f

Definition: Latent heat flux frequency and WPL corrected filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_LE_cw_f

Label: qc_LE_cw_f

Definition: qc value of LE_cw

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

LE_cw_gf

Label: LE_cw_gf

Definition: LE_cw_f gap-filled

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_LE_cw_gf

Label: qc_LE_cw_gf

Definition: qc value of LE_cw_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

H_c_f

Label: H_c_f

Definition: Sensible heat flux frequency corrected filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_H_c_f

Label: qc_H_c_f

Definition: qc value of H_c

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

H_c_gf

Label: H_c_gf

Definition: H_c_f gap-filled

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_H_c_gf

Label: qc_H_c_gf

Definition: qc value of H_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

UST

Label: UST

Definition: u star

Type: Physical quantity

Unit: meterPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

TAU_c

Label: TAU_c

Definition: Momentum flux frequency corrected

Type: Physical quantity

Unit: kilogramPerMeterPerSecondSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_TAU_c

Label: qc_TAU_c

Definition: qc value of TAU

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

TAU

Label: TAU

Definition: Uncorrected momentum flux

Type: Physical quantity

Unit: kilogramPerMeterPerSecondSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

TAU_FreqR

Label: TAU_FreqR

Definition: Frequency response of Tau

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

H

Label: H

Definition: Uncorrected sensible heat flux

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

H_FreqR

Label: H_FreqR

Definition: Frequency response of H

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

LE

Label: LE

Definition: Uncorrected latent heat flux

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

LE_FreqR

Label: LE_FreqR

Definition: Frequency response of LE

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

FC

Label: FC

Definition: Uncorrection CO2 flux

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

FC_FreqR

Label: FC_FreqR

Definition: Frequency response of FC

Type: Physical quantity

Unit: number

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Rg_f

Label: Rg_f

Definition: Downwelling short wave radiation filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Rg_gf

Label: Rg_gf

Definition: Rg_f gap-filled

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_Rg_gf

Label: qc_Rg_gf

Definition: qc value of Rg_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

VPD_f

Label: VPD_f

Definition: Vapor pressure deficit filtered

Type: Physical quantity

Unit: kilopascal

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

VPD_gf

Label: VPD_gf

Definition: VPD_f gap-filled

Type: Physical quantity

Unit: kilopascal

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_VPD_gf

Label: qc_VPD_gf

Definition: qc value of VPD_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

RH_f

Label: RH_f

Definition: Relative humidity filtered

Type: Physical quantity

Unit: percent

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

RH_gf

Label: RH_gf

Definition: RH_f gap-filled

Type: Physical quantity

Unit: percent

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_RH_gf

Label: qc_RH_gf

Definition: qc value of RH_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Ta_f

Label: Ta_f

Definition: Ambient air temperature filtered

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Ta_gf

Label: Ta_gf

Definition: Ta_f gap-filled

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_Ta_gf

Label: qc_Ta_gf

Definition: qc value of Ta_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Tsoil_f

Label: Tsoil_f

Definition: Surface soil temperature filtered

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Tsoil_gf

Label: Tsoil_gf

Definition: Tsoil_f gap-filled

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_Tsoil_gf

Label: qc_Tsoil_gf

Definition: qc value of Tsoil_gf

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

PA_1

Label: PA_1

Definition: Ambient atmospheric pressure

Type: Physical quantity

Unit: kilopascal

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Rg_out_f

Label: Rg_out_f

Definition: Upwelling short wave radiation

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

RNET_f

Label: RNET_f

Definition: Net radiation

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

PAR_f

Label: PAR_f

Definition: Downwelling photosynthetically active radiation

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

PAR_out_f

Label: PAR_out_f

Definition: Upwelling photosynthetically active radiation

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

PRECIP

Label: PRECIP

Definition: Rainfall

Type: Physical quantity

Unit: millimeter

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

SnowD_f

Label: SnowD_f

Definition: Snow Depth filtered

Type: Physical quantity

Unit: meter

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

G1_f

Label: G1_f

Definition: Ground heat flux filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

G2_f

Label: G2_f

Definition: Ground heat flux filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

G3_f

Label: G3_f

Definition: Ground heat flux filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

G4_f

Label: G4_f

Definition: Ground heat flux filtered

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

SWC_1_f

Label: SWC_1_f

Definition: Volumetric soil water content filtered

Type: Physical quantity

Unit: meterCubedPerMeterCubed

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

SWC_2_f

Label: SWC_2_f

Definition: Volumetric soil water content filtered

Type: Physical quantity

Unit: meterCubedPerMeterCubed

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Tsoil_2_f

Label: Tsoil_2_f

Definition: Surface soil temperature filtered

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

AGC

Label: AGC

Definition: AGC diagnostic

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

CO2

Label: CO2

Definition: Ambient CO2 concentration

Type: Physical quantity

Unit: micromolePerMole

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

ALBEDO_f

Label: ALBEDO_f

Definition: Albedo

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

WS_1

Label: WS_1

Definition: Wind speed

Type: Physical quantity

Unit: meterPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

WD

Label: WD

Definition: Wind direction

Type: Physical quantity

Unit: degree

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

cs616_1

Label: cs616_1

Definition: Raw probe signal

Type: Physical quantity

Unit: microsecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

cs616_2

Label: cs616_2

Definition: Raw probe signal

Type: Physical quantity

Unit: microsecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

PotRad

Label: PotRad

Definition: Potential Radiation

Type: Physical quantity

Unit: wattPerMeterSquared

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

FP_NEEnight

Label: FP_NEEnight

Definition: Nightime NEE for flux partitioning

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

FP_Temp

Label: FP_Temp

Definition: Air temperature for flux partitioning

Type: Physical quantity

Unit: celsius

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

E_0

Label: E_0

Definition: Temperature sensitivity coefficient of respiration

Type: Physical quantity

Unit: kelvin

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

R_ref

Label: R_ref

Definition: Reference respiration for partitioning

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Reco

Label: Reco

Definition: Ecosystem Respiration raw partitioned

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

Reco_f

Label: Reco_f

Definition: Ecosystem Respiration filtered partitioned

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

GPP

Label: GPP

Definition: GPP raw partitioned

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

GPP_f

Label: GPP_f

Definition: GPP filtered partitioned GPP

Type: Physical quantity

Unit: micromolePerMeterSquaredPerSecond

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

qc_GPP

Label: qc_GPP

Definition: qc value for partitioned GPP

Type: Physical quantity

Unit: dimensionless

Maximum: Not specified

Minimum: Not specified

Precision: Not specified

Missing values:

NaN = Missing or Not Measured

This material is based upon work supported by the National Science Foundation under Grants #DEB-1637459, 1026843, 9810222, 9211775, 8702328; #OPP-9911278, 9911681, 9732281, 9615411, 9615563, 9615942, 9615949, 9400722, 9415411, 9318529; #BSR 9019055, 8806635, 8507493. Any opinions, findings, conclusions, or recommendations expressed in the material are those of the author(s) and do not necessarily reflect the views of the National Science Foundation.